1. Field of the Invention
In general, the present invention relates to a process for cleaning debris, for example, sludge and/or construction debris.
More particularly, the present invention relates to a process for the treatment of materials containing water and contaminated with pollutants, the process using solvents. The inventive process has particular application to the treatment of sludge. However, the process can also be used on soil, sand, construction debris and other solid materials which are contaminated with pollutants.
2. Background Information
There is also a process for the extraction of impurities and toxic substances from soils in an extraction process which is performed on site, in which the material to be treated (i.e., soil) is extracted with non-flammable solvents, and the solvent is then recovered following the treatment by distillation. One disadvantage of this process is its use of certain solvents as extraction solvents, on one hand, because of the known toxicity of these materials, and on the other hand, because a complete removal of the solvents from the treated material cannot be guaranteed.
Using the existing processes, sludge from mining, industrial and commercial applications, have been solidified, primarily by mixing with additives, such as cement, calcium hydroxide or gypsum, and then either disposed of in landfills or used in road construction. However, on account of the high concentration of toxic substances, such disposal is no longer possible. Additionally, there are also bottlenecks in the allowable disposal by thermal means (e.g., incineration).
Due to the fact that space in landfills is becoming increasingly scarce, and in order to eliminate hazards to the environment, interest is currently being focused on processes for the separation of components which contain contaminates. The purpose of these processes is to reduce the volume of the waste and the concentration of the toxic substances, and to reuse, if possible, the purified material. Even in cases where reuse is not possible, the reduction in the volume of waste (e.g., by sludge dehydration and contaminant removal) saves valuable landfill space.
Contaminated materials can come from many diverse sources. For example, one well known source of such materials is the construction industry. Contaminants commonly find their way into the refuse piles on various construction sites. Moreover, the demolition of previously existing structures is an obvious source of materials which may have become polluted with contaminants and which therefore, often require that special precautions be taken in the treatment and disposal of the resultant debris. In particular, the demolition of previous manufacturing facilities often yields a great quantity of debris which is, or may be, contaminated with objectionable contaminants. Such contaminants are the result of the various supplies which are employed as a natural part of many and diverse manufacturing processes.
Still further, many manufacturing facilities, in and of themselves, generate considerable quantities of contaminated debris as a natural course of events in the ongoing manufacturing processes. Such debris is quite often not of such a nature that it is safely disposable without treatment to remove therefrom various contaminants which would be objectionable were the untreated debris to be directly disposed of in an untreated condition, for example, in a landfill.
It is clear that the land available for new landfills is becoming more and more scarce, existing landfill sites are becoming ever more overburdened. Therefore, there is an ever increasing interest in methods and processes which minimize the impact of waste and debris disposal upon the above-noted scarce landfill resources. Additionally, as noted above, there is an ever increasing concern that various contaminants not find their way into landfills, but rather be disposed of by more environmentally correct procedures. The present invention is directed towards addressing both of these concerns.
There is also a process for the extraction of impurities and toxic substances from soils in an extraction process which is performed on site, in which the material to be treated (i.e., soil) is extracted with non-flammable organic solvents, and the solvent is then recovered following the treatment by distillation. One disadvantage of this process is its use of chlorinated hydrocarbons as extraction solvents, on one hand, because of the known toxicity of these materials, and on the other hand, because a complete removal of the chlorinated hydrocarbons from the treated material cannot be guaranteed.
Using the existing processes, sludge containing oil, in particular from oil traps used in mining, industrial and commercial applications, have been solidified, primarily by mixing with additives, such as cement, calcium hydroxide or gypsum, and then either disposed of in landfills or used in road construction. However, on account of the high concentration of toxic substances, such disposal is no longer possible. Additionally, there are also bottlenecks in the allowable disposal by thermal means (e.g., incineration).
Due to the fact that space in landfills is becoming increasingly scarce, and in order to eliminate hazards to the environment, interest is currently being focused on processes for the separation of components containing oil. The purpose of these processes is to reduce the volume of the waste and the concentration of the toxic substances, and to reuse, if possible, the purified material. Even in cases where reuse is not possible, the reduction in the volume of waste (e.g., by sludge dehydration and oil removal) saves valuable landfill space.
Used hydraulic fluids, used oils and the contents of oil traps are types of waste which are commonly created in the coal mining industry and which must be disposed of. The waste substances contaminated with PCB/PCDM are normally separated in chemical-physical treatment facilities into a sludge, oil and water phase, which is reprocessed separately, in a so-called three-phase decanter. The end products are oil (contaminated by PCB/PCDM) for high temperature combustion, purified waste water and sludge (containing PCB/PCDM), which is normally solidified by the admixture of additives, for disposal in underground waste dumps.
Polychlorinated biphenyls (PCBS) and diphenylmethanes (PCDM) are synthetic oils which are particularly suitable for use in mining applications on account of their characteristics (they have very low flammability). After the entry into force of the Second PCB Guidelines in July of 1986, hydraulic fluids containing PCBs were replaced by PCDM (also called "HFD"), and other aqueous hydraulic fluids (e.g., HFA and HFC) not containing any PCB/PCDM. In spite of multiple changes and replacements of the hydraulic fluids containing PCBs during customary repair and maintenance activities, the oil destined for disposal may still contain residual concentrations of more than 100 ppm of these substances. Oils containing PCB are also encountered during the maintenance and cleaning of hydraulic equipment and machines, and in the disposal of large quantities of motor oil, and are therefore frequently also found in the oil traps of gasoline stations and vehicle repair shops.
The requirements for the residual oils concentration in waste which is to be dumped in landfills is certain to become stricter in the future, and corresponding rules regarding waste disposal are being prepared. To protect the waste disposal concept, for which it is essential, in the long term, that the residues be certified for disposal, attempts have therefore been made to find suitable treatment processes which will remove as much of the oil-containing components as possible. The present inventors have discovered that, by using the conventional washing processes, which work primarily with water and with the addition of surfactant substances (tensides), or with steam, it is extremely difficult, if not impossible, to achieve a sufficient separation of oil from the solids. This fact is believed to be due, on one hand, to the quality of the oil (high boiling point, non-volatility), and, on the other hand, to the high bonding forces between oil and solid, which cannot be sufficiently eliminated by the water treatment.